If this is your first visit, be sure to
check out the FAQ by clicking the
link above. You may have to register
before you can post: click the register link above to proceed. To start viewing messages,
select the forum that you want to visit from the selection below.

Vishnu Tuning finally managed to eek out a 10 second pass in their single turbo E92 335i that they were once touting would be in the 9's. After multiple unsuccessful attempts (with driver errors) from Vishnu owner Shiv Pathak he was able to get a high 10 second slip by raising the boost according to his data log and shifting cleanly. Details are scarce as Vishnu did not provide information on the youtube video upload and there also is no exterior view to show the slip actually correlates to the run shown in the video.

We will give the benefit of the doubt here but with all secrecy and the multiple attempts to get to this point the performance is simply underwhelming for the time and money investment. The car is said to have run 10.8@131. It recently was dyno'd at 627 wheel horsepower by Insideline so these horses are not translating well to the ground. This single turbo offers considerable lag and the top end pull for the sacrifice simply is not there especially compared to existing solutions such as the Rob Beck twin turbo upgrade which offers far greater spool and performance only a few miles per off through the traps but with far greater driveability.

The previous record was 11.10@127.21 with 19 psi of boost on the RB turbos. These turbos are a much more affordable option that also currently is available. Vishnu claims 23.5 psi of boost for this 10.8@131 mph run. Is it worth the minor top end benefit for the estimated $8500+ plus install? We do not think so and considering the way Vishnu hyped this the results are very underwhelming. The low end torque sacrifice is not being justified with a large top end gain.

We wish Vishnu luck in the future but for now this is still an experiment and work in progress that is tough to buy both figuratively and literally. There are more affordable options that work better for daily driven N54 vehicles that offer 97% of the performance in practice (as in not just a dyno queen) with less compromises. Not to mention for users to repeat what Vishnu has done here with their own single turbo it will likely be far more difficult as they will not have the option of risking their engine with higher boost and timing advances simply to try to eek out a tenth to squeeze past what already exists and get into the 10's. It may be a record, but it certainly is not impressive considering where the bar was already set with far less horsepower and much more affordable tuning and hardware options.

I think we all know Shiv is hiding some secret... what it is no one really knows. Why it hasn't been revealed as kits are already being sold is beyond me. There could be massive disappointments in store but in any case I am waiting to see what the smallest snail version can do.

Lol that's marketing but if he put down 644whp then 725hp@flywheel doesn't seem like an exaggeration.

Why would the transmission losses increase from 30 hp stock to 80+ hp tuned in a MT? The trap speed is not there either. We also need to keep in mind the car has very good tyres and extra pulling force due to a changed final gearing.

I think we all know Shiv is hiding some secret... what it is no one really knows. Why it hasn't been revealed as kits are already being sold is beyond me. There could be massive disappointments in store but in any case I am waiting to see what the smallest snail version can do.

Doubt there is any secret here. I think we can pretty much put the pieces together. As Cobb can take credit for finding out first with a DME flash you can open up a lot more room on the fueling side. More than many including myself thought possible only a few months ago. We've seen low fuel pressure drops in the past so I'm sure a new in tank pump or booster pump is part of the equation. And then a turbo that can flow enough to allow peak HP @ peak RPM where VE is theoretically the highest. Surprised the o2 sensors are holding up with the preturbo positioning but until more customers are running it we won't get any independent data on that. If that o2 sensor position is workable then Vishnu can take credit for doing it first. It certainly makes manifold design a lot easier / less expensive. IMHO they should add an oil catch can of some sort and rework the turbo filter, maybe do a custom one for more surface area, to allow longer service intervals. Perhaps the filter setup is also part of the reason the dyno numbers and track MPH don't quite add up.

@Terry@BMS, obviously, this is only a V1...there will probably be a v2, a v3, v3 rev1/rev2/2a/2b/3...think next year we'll have the option that actually truly performs when it comes to TRAPS, which, I totally don't understand for the power put down...

Why would the transmission losses increase from 30 hp stock to 80+ hp tuned in a MT?

really dude? the tranny loss is a percentage. look, the stock n54 fly hp numbers are 300/300 right? which then taking ~15% of that (MT) leaves you with ~255wheel. ~45hp loss. now a single turbo set up. ~645wheel, add 15%. 741flywheel/crank hp. so look at the math. as the hp numbers go up, the percentage of drivetrain loss makes the difference between wheel and crank hp increase as well. get it?

really dude? the tranny loss is a percentage. look, the stock n54 fly hp numbers are 300/300 right? which then taking ~15% of that (MT) leaves you with ~255wheel. ~45hp loss. now a single turbo set up. ~645wheel, add 15%. 741flywheel/crank hp. so look at the math. as the hp numbers go up, the percentage of drivetrain loss makes the difference between wheel and crank hp increase as well. get it?

The transmission loss is a precentage. But it is not proportional to a power increase. Dude.

The transmission loss is a precentage. But it is not proportional to a power increase. Dude.

think about what you're saying. of course it is proportional to power increase. lets take more extreme examples. a honda civic and a drag/funny car. the honda makes 200hp at the flywheel. to measure wheel hp take away 15% for a MT right? 170wheel. so a 30hp difference. ok. now a funny car. 8000hp measured at the crank i believe. 15% drivetrain loss (though they probably have more/less) to be consistent, would be 1200hp lost due to the transmission. so 6800wheel lol. so 30 versus 1200. is that clear now?

The transmission loss is a precentage. But it is not proportional to a power increase. Dude.

I'm with @R1000K3 on this one..while a percentage CAN be calculated, definitely isnt and doesnt need to be linear...why would it be? Mechanical losses arent linear with power made so a static 15 or 18 or whatever percentage is a bad approximation as its only a percentage of drivetrain loss at stock power levels and thats it...marketing loves to use it obviously!!

I'm with @R1000K3 on this one..while a percentage CAN be calculated, definitely isnt and doesnt need to be linear...why would it be? Mechanical losses arent linear with power made so a static 15 or 18 or whatever percentage is a bad approximation..

hey i'm no mech engineer so don't take my word as stone. would love to pose this question at someone we have here like dbfiu. he works will insane sized turbines so i'm sure he knows a thing or two about frictional losses.

Drivetrain losses is not a fixed percentage, but it is not a fixed HP either. High powered cars have heavy duty transmissions and larger total contact areas, so if you think of civic vs a high powered car, the percentages can be close. however, if you have a stock N54 transmission, and have the same transmission but tuned the engine to >double the whp, the transmission losses do not suddenly go up by the same multiplier as the power.

Some examples, let's say you drive your N54 at steady 65MPH. The WHP reserve of the engine has does not affect the transmission losses at all. If you drive steady 75MPH, the transmission losses increase as they are affected by the speed quite a lot. Drivetrain losses depend on the gear, RPM, torque.....

Drivetrain losses is not a fixed percentage, but it is not a fixed HP either. High powered cars have heavy duty transmissions and larger total contact areas, so if you think of civic vs a high powered car, the percentages can be close. however, if you have a stock N54 transmission, and have the same transmission but tuned the engine to >double the whp, the transmission losses do not suddenly go up by the same multiplier as the power.

Some examples, let's say you drive your N54 at steady 65MPH. The WHP reserve of the engine has does not affect the transmission losses at all. If you drive steady 75MPH, the transmission losses increase as they are affected by the speed quite a lot. Drivetrain losses depend on the gear, RPM, torque.....

They don't go up the exact same as the power does but they do go up. I see this all the time with drag motors, they'll make say 1900hp@crank then go in a car with a th400 and a ford 9" rear and lose 250hp+ and that's with everything as lightweight as possible in both the Trans and the rear. Do you think the th400 and ford rear cost their original cars that much power?

hey i'm no mech engineer so don't take my word as stone. would love to pose this question at someone we have here like dbfiu. he works will insane sized turbines so i'm sure he knows a thing or two about frictional losses.

The frictional losses are about the same unless the oil film collapses. What will change is mainly just the heat in the transmission for a car when the power is increased and the power band is the same. In case the RPM is increased it will increase transmission losses more, but not at a fixed percentage. Crank power is measured in a bench test. You cannot calculate the crank power correctly from wheel horses.

I think most people agree a Top Fuel transmission consumes more power than a Fiat Uno as you say. But do they really use the same transmission .

They don't go up the exact same as the power does but they do go up. I see this all the time with drag motors, they'll make say 1900hp@crank then go in a car with a th400 and a ford 9" rear and lose 250hp+ and that's with everything as lightweight as possible in both the Trans and the rear. Do you think the th400 and ford rear cost their original cars that much power?

As I said, and as you said, the losses in whp go up as power goes up, but not as a fixed percentage

I think everyone is a little right and a little wrong on figuring out the loss of hp from crank to wheel. If we combine everyone's answers we may be able to get a better one. First question we have to ask is: what causes hp loss from crank to wheel and how is this relationship changed when going from a smaller hp to a larger hp?

HP loss is caused by many things but here are some: 1. moment of inertia from all the engine parts that transmit power from the cylinders to the wheels - this is unchanged from lower hp to higher hp (moment of inertia is based on the geometry, mass, and axis of orientation of the each piece, so it goes against a fixed percentage loss. 2. Rotational frictional losses due to viscosity. This force is related to the viscosity of the substance, the area of contact and the velocity gradient. The frictional forces would increase with more hp as you are increasing the velocity gradient - this tends to backup the idea of a percentage loss. But you must also factor in that motor oil is shear thinning meaning that the more shear you place on it (i.e. more hp turning the parts) the less its viscosity and frictional force opposing are. This tends to dilute the percentage theory. 3. Inefficiencies shown through more heat creation. Energy gets converted into work done outside the system or heat lost outside the system. More hp tends to yield more heat lost outside the system. This would backup the percentage idea.

The toughest part is knowing how all these relate to each other. It's tough to say that it's black or white. My opinion - the same percentage loss will not apply to the same engine at different power levels. The rotational mass is unchanged so I'd believe that the percentage would be less at higher HP levels. This is probably hard to test in theory, and more than likely can only be empirically proved, so I will leave it as just my opinion. What is everyone else's technical thoughts?